Machine gun trigger mechanism



. March 11,1958 N. A. DQDICH MACHINE GUN TRQIGGER MECHANISM Filed April 29. 1954 IN VEN TOR. /V/CHOA,45 19. OQD/CH BY A TTOENE Y be required under many conditions. gpresent machine gun should be mounted in many locauseful in combat.

United States Patent MACHINE GUN TRIGGER MECHANISM Nicholas A. Dodich, Waukesha, Wis.

Application April 29, 1954, Serial No. 426,322

9 Claims. (Cl. 89-140) This invention relates to improvements in a firing or trigger mechanism for machine guns and especially for guns of the Browning type and of the general construction of such gun as known to the U. S. Dept. of Defense as the M1919.

The present Browning machine guns are capable only of automatic or continuous fire after the trigger has been .once pulled and so long as ammunition is supplied. In

training, an effort is made to minimize the number of shots per burst to conserve ammunition and targets, to reduce gun wear, to save time and for other reasons. The gun can actually be aimed only for the first shot and the trajectory of the remaining shots in any firing burst, depends on stability of the gun support, uniformity of ammunition, degree of wear and maintenance of the gun and other factors which are not controllable during firing. Even trained soldiers find it diificult to fire short bursts or bursts of the same number of shots.

Hence, the teaching of soldier trainees at present is to zfire bursts of about six shots each. As a matter of fact,

the score card used in the training for machine gun marksmanship specifies 6-round bursts for a part of But the number of shots per burst of period, with large savings in many factors but especially in the ammunition used in practice.

In actual combat, only occasional single shots may However, the

tions where only single shot fire will be required for a large part of the timebut where reserve fire power is highly important and where such reserve fire power could be furnished by the automatic fire of a machine gun adapted to single shot fire also, by use of the present invention.- Ability to fire single shots at will or as desired, would prevent immediate detection of the machine gun placements and prevention of such detection is very The possibility of firing single shots and of full automatic fire has other advantages in combat .which will readily appear to anyone with military training or experience, or both.

One particularly important use to which the present invention is applicable is in connection with both training and actual combat use of tanks. The trajectory of bullets fired by machine guns mounted in tanks, is similar to that of the shells fired by the 90 mm. cannon of tanks. Therefore, if equipped with the present trigger mechanism, a machine gun 'mounted in a tank could bracket" or zero-in a target and thus furnish a guide for setting range, elevation, etc. of the cannon in shorter time and at less cost than at present for training and would have obvious advantages in combat.

. It is therefore an object of'the present invention to -.provide a trigger mechanism for a machine gun and which 2,826,121 Patented Mar. 11, 1958 ice will permit single shot or automatic fire by the gunner as he desires, and with substantially no time lag between shifting from one kind of firing to the other.

Another object of the invention is to provide a trigger mechanism for machine guns which may be utilized as a replacement for the present trigger, and without change in the gun itself other than removal of the present trigger, and insertion of the mechanism of the present invention while allowing either single shot or automatic tire of the machine gun.

Another object of the invention is to provide a trigger sub-assembly for placement in present machine guns especially of the Browning or military M1919 type and in which the operation of the replacement mechanism is so slightly different from that of the present trigger mechanism, as to be immediately usable by anyone having training only with present machine gun triggers.

Objects and advantages other than those above set forth will be apparent from the following description when read in connection with the accompanying drawing in which:

Fig. l is a fragmentary side elevation of a M1919 Browning machine gun with parts broken away to illustrate the present trigger mechanism or sub-assembly in place and its operative relations to standard and unchanged parts of the machine gun.

Fig. 2 is a perspective view of the present trigger subassembly.

Fig. 3 is a top plan view of the present trigger subassembly; and

Fig. 4 is a side elevation of the improved trigger mechanism with portions thereof cut away to disclose parts of the mechanism which are at least partially enclosed in other parts of the sub-assembly.

The Browning or M1919 machine gun is recoil operated, that is, each time a cartridge is fired, the recoil pulls the gun barrel back a short distance. Backward movement of the barrel unlocks the bolt and forces the bolt back against the pressure of a spring. The backward movement of the bolt extracts the empty cartridge case from the firing chamber, ejects the empty cartridge case and draws a live cartridge out of the ammunition belt. The spring (with the assistance of other spring actuated parts) then returns the bolt to load the cartridge into the barrel chamber, presses the barrel to forward position and locks the bolt to the barrel. Another spring then acts on the firing pin to fire the cartridge.

The reference numeral 10 designates the extension of the gun barrel which engages the breech lock 11, the breech lock 11 having a pin at 12 and being in turn engageable with the arms extending from the breech lock frame group (the trigger housing). An accelerator 20 includes a pin 21 on which is mounted a cam 22. A spring 28 acts on the accelerator to produce the final forward movement of parts and on the lock 11 to lock the bolt in firing position.

The bolt 30 carries the firing pin 31, and the bolt and firing pin action is controlled by a sear 32. The cocking lever 36 is pivoted for engagement by the bolt and the firing pin. The above parts are under the action of springs, of which driving spring 37, compressed upon recoil of the barrel, furnishes the power by which a cartridge is extracted from the ammunition belt, loaded into the chamber and the firing pin is cocked. The firing pin is driven by its own spring which is associated with the cocking lever as is well known and not illustrated. v

In the present modification for replacing the usual trigger, a trigger unit comprises a trigger body generally designated 49. The trigger body is pivoted in the gun at 50 on a pivot pin fixed in the gun housing inclosing some of the above parts for mounting the usual trigger, which has a longitudinal slot in which otherparts ofthe asaenat 3. gtrigger,subassemblyare mounted and capable of movement relative to the triggerbody, the trigger body having a forward or nose end 51, and a trigger finger grip portion 52 at the other end, of the usual shape and accessible from outside of the housing inclosing the above gun parts. A trigger bar 53 is'pivoted in thetrigger-body at 54 and has a hook-like rearwardportion-55inside the trigger body slot. The trigger bar extends from'the trigger body slotover the nose end 51 thereof and to the position where cam extensions 56 may engage with the firing pin sear 32.

A sear 60 is pivoted at 61 in the trigger body-and has a hook-like end 62 inside the trigger body slot and engageable with the trigger bar hook 55, the other end of the sear being formed as a substantially rectangular U- .shapedfork 63. A pin 67 extends through the trigger body for mounting thereon of a spring 68 having its ends bar together or. releasing such bar for movement relative to the trigger body, and from adjacent the trigger grip.

A selector member 73 is shown as a bar. slidable in the rearward portion of the trigger body slot. Theselector is retained in position partly by a pin 74 passing through the trigger body and through a slot in the selector, and partly by a pin 75 through the trigger body either above the selector, as shown, or through another slot therein in the trigger body grip portion. It will be noted that the selector is formed with a pair of notches 76, 77 in the upper edge thereof and toward the selector slot receiving pin 74. The notches are placed for'locking trig- -.ger..bar.53 against trigger body 49 or to allow relative movementstherebetween.

A spring 80 is mounted on a pin 81 extending from one side of thetrigger body and the ends of the spring bear severally on a pin 83 extending from the breech lock frame, and in either notch 76 or 77 in the selector member. A pawl or other type of detent.,may be used in lieu ofthe spring if such detentmayshift into or out of engagement with the selector upon pressure or a. pull thereon.

It will be understood that the usual M1919 machine gun trigger and its safety lock has a general shape which is followed in outline by the present construction, and that the dimensions of the present trigger unit and which must cooperate with other standard parts of the gun, are the same as in the standard trigger.

Assuming that thegun is loaded, the automatic or 2 multiple shot operating sequence of the usual M1919 is as follows: .a pull onthe trigger releases sear 32 and the firing pin 31 isdriven forward by the firing pin spring -(not shown), to fire the cartridge then in the barrel chamber. The barrel then recoils and barrel extension 10, breechlock 11 and bolt 30 are moved backward. The

breech lock pin 12strikes an inclined surface on the breech lock frame which unlocks the bolt from the barrel extension. Recoil of. the barrel extension acts on one .surface of the accelerator 20 and forces the accelerator backwardly so that another surface of the accelerator .engages the bolt 30'to release it from the barrel and to force thebolt backward against'the action of the spring 37. .-.--.As the bolt30 moves backward, theextractor draws a ."axtartridge .from the .ammunition belt and the extractor iorces the cartridge down into a groove in the bolt. rvAt-thesametime, the-ejector pushes the empty. cartridge .case downnthroughsthe. bolt and the empty casedrops to therground. eithefiring pin'31 iscocked by the cocking lever 36 as the bolt movesbackward. At the same time a lever for feeding the ammunition belt, rides in its cam groove in the top of the bolt and moves the belt feed pawl to engage the pawl behind the next cartridge. While the next cartridge is being engaged, the ammunition belt is held in place by another pawl.

When the backward motions of the various parts of the gun are completed, the driving spring 37 forces the bolt 30 forward, A groove in the surface oftheejector places the cartridge in the bolt in the correct position for entry of the cartridge into the barrel chamber. After the cartridge has entered the firing chamber, the extractor cam plunger raises the extractor, the ejector having now reached the clearance cut-in thesideof the barrel extension to swing out and pass the cartridge.

As the bolt 30 approaches the end of its forward motion, it moves the barrel extension 10 and the breech lock 11 forward and forces the breech lock to ridejon the ,breech lock. cam and engagebehind a shoulder in; the

bolt tolock the bolt to the barrel extension. If the present trigger were now held back by the gunner, projections on the sear 32 would engage under one of cam surfaces 56 on the end of the trigger bar 53 and thesear 32 would rider downwardly thereby releasing the firing pin and causing the cartridge tobe fired, which completes the cycle of actions.

.When the present construction is to to be fired single shot or semi-automatic fire, the selector 73 is pulled backward and the, forward end thereof is then disengaged from under the trigger bar 53-55 to provide a 7 spaced between the selector and the trigger bar. That end of spring engaging with the selector, now rests in notch 77 and holds the selector out of contact with the trigger bar 53 which may now pivot clockwise relative to the trigger body 49 upon release of the trigger sear 62. When .the trigger 52 is pulled, the trigger bar 53 releases the sear 32 so that the weapon may fire single shot as is described below.

As the barrel etc. and the bolt 30 recoil, the bolt engages sear fork 63 and presses the sear 60 counter-clockwise to release its hook end 62 from the hook end 55 of the trigger bar. The spring 68 then forces the trigger bar 53 to rotate counter-clockwise about its pivot 54 so that the firing pin sear 32 will not be engaged by the trigger bar and be released on occurrence of the counter-recoil force. To fire the weapon again, the finger pressure on the trigger grip 52 is first released. The spring 80 then reacts on the pin 83 to force the trigger unit to rotate counter-clockwise whereupon spring 68 swings trigger sear 60 to re-engage its hook end 62' with the hook end 55 of the trigger bar.

'When an M1919 machine gun equipped with the presenttriggerunit is to be fired as a full automatic, theselector 73 is. pushedforward and the forward end thereof engages a surface on the under side (under the hook portion 55) of thetrigger bar 53 which locks the trigger bar against counter-clockwise movement. The end of the spring'80 then seats in-selector notch 76 and holds theselectorand the trigger bar against movement relative to the trigger body. The trigger mechanism new acts as asingleunit precisely as is the case when thestandard trigger is used.

The parts making up the present mechanism should, of course, be made as 'forgings and otherwise as is usual for firearms and. of high grade materials to secure satisfactory durability. However,-even a working model made OfDfdiIlfiI'Y steel and withrnakeshift springs, and by aperson not-trained in workingmetals or as a gun- .smith,.oper-ated mechanically without malfunctions 'ina :were nodnstances when the mechanism failed to functtionasdesired and only onesinstance per 55- shots where the mechanism failed to function substantially as smoothly as the original machine gun trigger.

; From the above description, it will be apparent that the trigger sub-assembly of this invention is interchangeable in the field with the standard M1919 machine gun trigger and with only such tools as are customarily used for disassembly and re-assemblyof such gun. No changes whatever are made in clearances or otherwise in the machine gun parts with which the present trigger mechanism coacts. Hence, the advantages stated for both the training of soldiers and used the gun in combat, and other advantages not specifically enumerated, are immediately applicable to all M1919 guns in existence.

' Although the present inventionhas been embodied in an assembly specifically applicable: to the Colt embodiment of the Browning design of machine gun, it will be apparent to anyone skilled in the art of gunsmithing, or experienced in the handling of firearms and particularly machine guns, that the present invention is adaptable with only minor changes in various parts, to any machine gun now 1n use.

. The present trigger sub-assembly has four major components, namely, a longitudinally slotted trigger body with a trigger grip portion, a trigger bar pivoted on the trigger body and extending from the slot therein for engagement with the firing pin sear and having a hooked portioninside the trigger body slot, manually operable selector means for alternatively holding the trigger bar on or releasing the trigger bar from the trigger body (for movement relative to the trigger body, and trigger sear means releasable from-and re-engageable with the trigger bar (after. the selector means has released the trigger bar). A slight pull on the selector bar is sulficient to unlock the trigger bar when single shot fire is desired. Each single shot now requires pulling of the trigger and release of the trigger for return of the trigger bar to the position for another shot and results in automatic disengagement and re-engagement of the trigger sear and trigger bar. For conversion from single shot fire to automatic fire, the selector bar is pushed to lock the trigger bar against movement relative to the trigger body. During single shot fire the trigger sear is automatically released from and re-e'ngaged with the trigger bar but such action is now impossible and the entire trigger mechanism acts as a unit.

Although but one embodiment of the present invention has been illustrated and described, it will be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit of the invention or from the scope of the appended claims.

I claim:

1. In a trigger mechanism for automatic and single shot firing of a machine gun as selected by the gunner, said machine gun including a firing pin and a trigger pivot pin and a sear for the firing pin, a trigger body pivotal on the gun trigger pivot pin, a trigger bar pivoted on the trigger body and engageable with the firing pin sear, sear means pivoted on the trigger body for releasably holding the trigger bar in given relation with the trigger body for movement therewith in automatic fire of the machine gun, and selector means mounted on the trigger body and manually reciprocable for holding and for releasing the trigger bar respectively from and for movement relative to the trigger body for semi-automatic fire of the machine gun responsive to actuation of the trigger mechanism by the gunner.

2. In a trigger mechanism for automatic and single shot firing of a machine gun as selected by the gunner, said machine gun including a firing pin and a trigger pivot pin and a sear for the firing pin, a trigger body pivoted on the gun trigger pivot pin and with a trigger grip portion accessible from exteriorly of the gun, a trigger bar pivoted on and extending beyond the trigger body for engagement with the firingpin sear, trigger sear means pivoted on thetrigger body for holding the trigger bar against the trigger body formovement therewith in automatic fire of the machine gun, and selector means mounted on the trigger body and manually operable for release of the trigger bar from the trigger sear means and movement of the trigger bar relative to the trigger body for single shot. firing of the machine gun upon voluntary movement of the trigger mechanism by the gunner. I

3. In a trigger mechanism for automatic and single shot firing of a machine gun as selected by the gunner, said machine gun including a firing pin and a trigger pivot pin and a scar for the firing pin, a trigger body pivoted on the trigger pivot pin, and having alongitudinal slot therein, a trigger bar pivoted in the trigger body slot and extending over the forward end of the trigger body for engagement with the firing pin sear, sear means pivoted on the trigger body for holding the trigger bar in given relation with and for movement with the triger body in automatic fire of the machine gun, and selector means mounted on the trigger body and manually operable for releasing the trigger bar for movement relative to the trigger body for single shot firing of the machine gun upon movement of the trigger mechanism by the gunner.

4. In a trigger mechanism for automatic and single shot firing of a machine gun as selected by the gunner, said machine gun including a firing pin and a trigger pivot pin and a sear for the firing pin, a trigger body pivotal on the gun trigger pivot pin, a trigger bar pivoted on the trigger body andengageable with the firing pin sear, a sear pivoted on the trigger body and engageable with the trigger bar for releasably holding the trigger bar in given relation with the trigger body for movement therewith in one firing condition of the machine gun, spring means for urging the last-mentioned sear toward the trigger bar, and selector means mounted on the trigger body and manually operable for locking the trigger bar against movement relative to the trigger body in another firing condition of the machine gun.

5. In a trigger mechanism operable both for automatic and for single shot firing of a machine gun as selected by the gunner, said machine gun including a firing pin and a trigger pivot pin and a sear for the firing pin, a trigger body pivotal on the gun trigger pivot pin, a trigger bar pivoted on the trigger body and engageable with the firing pin sear, the trigger bar having a hooked end remote from the firing pin sear, a sear having a hooked portion and pivoted on the trigger body for movement of the sear hooked portion into engagement with the hooked end of the trigger bar, spring means tending to rotate the last-mentioned sear about its pivot for hooking the trigger bar with the trigger scar, and selector means mounted on the trigger body and manually operable for releasing the trigger scar and the trigger bar whereby trigger bar movement relative to the trigger body causes single shot firing of the machine gun responsive to actuation of the trigger mechanism by the gunner.

6. In a trigger mechanism convertible from automatic to single shot firing, and vice versa, of a machine gun as selected by the gunner, said machine gun including a firing pin and a trigger pivot pin and a sear for the firing pin and a gun bolt, a trigger body pivotal on the gun trigger pivot pin, a trigger bar pivoted on the trigger body and engageable with the firing pin sear, a scar pivoted on the trigger body and movable for engagement with the trigger bar, and selector means mounted on the trigger body and manually operable for releasing the trigger bar for movement relative to the trigger body for single shot firing of the machine gun upon movement of the trigger mechanism by the gunner, the scar on the trigger body having a portion engageable by the gun bolt for releasing the t j 'ger sear fron'r'the trigger ban upon each recoil ofv thefgun. I

7. In a'trigger mechanism for-automatic and-single shot firing of a machine gun as selected by the -gunner, said machine gun'including a firing pin 'and -a trigger pivot pin and a scar for the firing pin, ajtrigger'body pivotal onthe gun trigger pivot pin, a tniggerbarpivoted onthe trigger body and engageable vyiththe 'firing pin sear,

selector means for locking the trigger-baringiven-relation with the trigger body for movement therewith in automatic fire of the machine-gun,-a detent engageable with the-selector in one of a plurality ofp'osit-ionsselected by the gunner andtcorrespondingto automatiofire position andsingle shot fire relations-of the trigger bodyand trigger bar, and means pivoted OILithe trigger-body for sequentially engaging and releasing the tri'gger bar-from :the trigger body upon single shot fireof the gun.

8. In a trigger mechanism for selective-automatic firing and single shot firing of .a machine guny saidmachine gun including a firing pin-and a trigger pivot pin and a sear for the firing pin, aitrigger body pivotalvon the gun trigger pivot pin, theitriggertbodyihaving.a slot therein, atrigger bar pivoted .on thetrliggerth'ody and eugageable with the firing pin sear, aselectombarsselectively and manually operable for holdingzthentrigger bar in given relation with the trigger body fornmpvement therewithin automaticrfire of the machine gun,;the selectorbar-being. slidable in the trigger bodyislotaintozand out of engagement withtthe trigger bar andyhavingaplurality of notches; severally corresponding to. conditions for relative movement of the triggerbody and the triggerrbar and for maintaining 'the trigger bar in given; relation with the trigger body, and a detent engageable-avithone of the selector bar notches, wherebyselective firing of vthe machinegun automatically or at willgisobtained.

- 9.In a trigger mechanismfor selective automatic firing and semi-automatic-firing of a machine gun, said machine gun including a trigger pivot pin anda scar for the-firing pin and an abutment for a spring, a trigger body :pivotally mounted on the trigger pivotpin and having pivoted on thetrigger-body for urging saidsear toward engagement with 1 the: trigger bar, a selector mounted in the slot'inthe trigger body and slidable intoand out of engagement with the: trigger bar, and a springrreleasably -engageablewith ;theselector in any one of. a number of ,positions ;and'- acting; between ,the abutmentvtherefor: and

the selector whereby the trigger bar andtriggerlsear are held inengagement lHKOIlCgSClfiCtOI' spring position. and

are releasable in; another selector springposition forautomatic, fire-,and"semi automatic ifire respectively of the m hine-g -References Cited in the file of :this patent LUNITEDf STATES BAT N 1,475,761 :rFisher *Nov. 27, 1923 1,563,751 :Kewish v -Dec. 1,1925 1,-587j003 t Kewish June 1, 1926 42,119,536 qGreen June 7, 1938 2,311,012 Woodhull z Mar. 6,1945 2,385,057 'Browning .4 I Sept.18, 1945 

